Federal safety requirements require vehicles to withstand loads on the vehicle roof area for occupant safety and protection. These load requirements, expressed as a percentage of vehicle weight, increase as newer Federal requirements are established. The roof load requirements are intended to simulate loads on the vehicle encountered during a vehicle rollover event. The newer, more demanding Federal requirements force countermeasures, i.e. changes to the structure of vehicle frames, which can ultimately add significant cost and weight to the vehicle. It is essential to minimize the weight of the vehicle, and thus the countermeasures adopted to meet the newer Federal safety requirements, as added weight to the vehicle frame translates into increased load requirements as the requirements are expressed in terms of a percentage of the total vehicle weight. Increasing frame size is, therefore, a “Catch 22” type of situation in that the addition of structure to meet the load requirements of the newer regulations results in increased load requirements that must be resisted by the frame structure to satisfy the Federal requirements.
One of the challenges in maintaining frame integrity to withstand the crush loads imposed on the roof structure is the formation of the joints between respective frame members. If the joints separate during crush loading, the frame will undergo collapse before the respective frame members are crushed. Accordingly, improvements in the formation of structural joints would present an opportunity for increasing the load carrying capability of the automotive frame structure.
In U.S. Pat. No. 4,618,163, granted to Franz Hasler, et al on Oct. 21, 1986, the automotive frame is formed with internesting members, including joints that are used to interconnect frame members extending in different directions. In this manner, the respective frame members are tied together by the joint members. The automotive frame in U.S. Pat. No. 4,355,844, issued to Marco Fantini Muzzarelli on Oct. 26, 1982, is made in a similar manner with joint connectors placed to engage frame members extending in different directions to tie the automotive frame together. The joint connectors are formed of three shell elements, two of which are L-shaped and the third may be formed by an independent element.
A similar space frame construction for an automotive frame is disclosed in U.S. Pat. No. 4,660,345, issued on Apr. 28, 1987, to James Browning, in which thin walled castings are welded together to form a unitary, multiple pipe juncture between series of truss or elongated structural members, forming the vehicle space frame. The space frame concept is expanded in U.S. Pat. No. 5,715,643, granted on Feb. 10, 1998, to Raymond Parkinson, in which a joining system is disclosed for joining automotive chassis members together to form a space frame structure.
It would be desirable to provide a configuration for forming a joint between frame members in an automotive frame that will improve the load carrying capability of the automotive frame.